1. Field of the Invention
This relates to evaporative cooler apparatus and, more particularly to a dual pump system for evaporative coolers in which a primary pump is used to supply water to an evaporative medium, and a secondary pump is used to drain the water pan of the evaporative cooler.
2. Description of the Prior Art
Evaporative cooler pumps have been known for many years. Typically, a single pump is used in an evaporative cooler to provide water for soaking an evaporative medium through which air is forced. The air is cooled evaporatively by giving up the latent heat of evaporation to the water in the evaporative medium.
An inherent problem with evaporative cooler pumps of the prior art is their limitation of pumping efficiently when the water level in the pan at the bottom of the evaporative cooler drops below a certain amount, which is typically an inch or so. As the water level decreases, there is cavitation caused by the pump design, namely the impeller of the pump, and the pump loses efficiency. Air is introduced into the stream of pumped water due to impeller cavitation, and the flow rate efficiency of the pump drops substantially.
The evaporative cooler pump of the present invention includes an impeller design which greatly enhances the pumping flow rate efficiency by decreasing the cavitation and accordingly allowing the water level to drop substantially below that which is usable in the prior art pumps, and still pumping efficiently without air bubbles in the pump water line.
A second feature of the pump apparatus of the present invention is the utilization of a secondary pump to periodically drain the evaporative cooler.
To decrease the dissolved solids (or salt) content of water used by evaporative coolers, a bleed system has been utilized by which a portion of the pumped water is continually bled off and drained out of the evaporative cooler. This requires the continual addition of new water to the evaporative cooler on a regular basis to replace the water that has bled off. The introduction of the fresh make-up water decreases the salt concentration content of the water in the cooler sump.
Since some of the water pumped to the evaporative medium drains down and returns to the sump, or bottom, of the evaporative cooler, that water includes the salt originally present in the water, and the build up of salts in the cooler, and on the evaporative medium, causes a loss of efficiency of the evaporative medium and a buildup of the salts in the evaporative cooler housing itself. The continuous bleedoff of the water requires the introduction of fresh water to help decrease the salinity concentration. On the other hand, the continuous bleedoff wastes a substantial amount of water.
A secondary pump, a drain pump, in the evaporative cooler apparatus of the present invention substantially decreases the waste of the water, such as heretofore bled off, by periodically draining the sump or bottom portion of evaporative cooler housing, thus allowing for the introduction of fresh water on a periodic basis. This provides at least two advantages. The first advantage is the use of less water than the prior art continual bleed systems, and a decrease in the salinity of the water due to the replenishment of the water on a regular basis.
A timer is used to actuate the drain pump on a regular basis. The salt or mineral buildup decreases, and the periodic changing of the water prevents a buildup or accumulation of stagnant water, and accordingly, there is a substantially decreased possibility of the breeding of mosquitoes in the evaporative cooler.